The invention represents an improvement over existing fragrance diffuser systems, otherwise known as “reed diffusers”. The aforementioned systems are composed of a number of reeds (usually 5 to 12), fragrance oil, and a fragrance oil reservoir. Reed diffusers deliver fragrance to the atmosphere through the processes of adsorption and desorption (diffusion). For operation, a reservoir is filled, typically half-full, with a fragrance oil composition and reeds are placed in the reservoir. The lower portions of the reeds are submerged in the reservoir and the upper portions are exposed to the atmosphere. The fragrance oil is absorbed into the lower portions of the reeds and travels to the upper portions through capillary action. In this manner the entire length of the reed is saturated with fragrance oil. Once the reeds are saturated, and to some extent during the saturation process, the fragrance oil desorbs from the reeds and diffuses into the surrounding atmosphere, delivering the fragrance.
The reeds are natural products and are typically obtained from rattan, willow, or similar plants which, when dried, are capable of absorbing, wicking, and diffusing liquids. The reeds are typically selected to have a diameter of ˜0.10″ and are cut to 12.0″ lengths.
Since the reeds are natural products, their properties, such as wicking speed, absorption capacity, and shape are inherent to the plant from which they are obtained and cannot be easily modified or optimized for a particular application. Consequently, other than being aesthetically pleasing, the natural reeds are poorly suited for use in fragrance diffusion.
A major limitation of natural reeds is their wicking rate. Other than ambient effects (i.e. air flow, temperature, etc.) the most important factor in the functioning of reed diffusers is the rate at which the fragrance oil is drawn from the reservoir and brought into contact with the ambient atmosphere (wicking rate). Once the reeds are placed in the fragrance oil, it typically requires 36-48 hours for the reeds to become totally saturated and to function at full capacity. This slow wicking rate (3.2×10−2 ml/hour) negatively affects the reeds functionality as a fragrance diffusing device. Another important factor in fragrance diffusing is the amount of fragrance oil that is in contact with the surrounding atmosphere. This parameter is controlled by the surface area, and more importantly the surface area to volume ratio, of the diffusing device. Natural reeds have an extremely low surface area to volume ratio (0.064 cm2/cm3 (lateral surface area/volume)), which is also a factor in their poor functionality. Also, the shape of the reeds is limited to a cylindrical shape due to the morphology of the plant from which they are obtained, which results in a relatively unchangeable surface area to volume ratio. These combined limitations result in a poor rate of fragrance diffusion of ˜0.09 g/hr per reed (1.08 g/hr for the typical set of 12). Finally, the slow diffusion rate results in higher manufacturing costs due to the need for increased fragrance concentration in the fragrance oil. To compensate for the low diffusion rate, the fragrance, which is the most costly portion of the fragrance oil, is typically maintained at 15 wt % of the reed diffuser fragrance oil composition.
Standard porous ceramics, such as porous cordierite, have been used in various fragrance diffusion systems. However, they have seen limited use due to low wicking rates and their innate brittleness when formed into shapes with a high aspect ratio. To be effective at absorbing liquids, such as fragrance oils, the ceramic body must be highly porous. Unfortunately, higher porosity also leads to decreased strength of the ceramic body. To be used effectively as a wick, porous ceramics should have an open porosity of greater than 40% of the ceramic body, however, once the porosity is greater than ˜30%, the ceramic body is too weak to be used as a wick. Additionally, even with >40% porosity, the wicking rate is exceptionally slow (2.0×10−2 mL/hour). These limitations make conventional porous ceramics unsuitable for use as wicks.
Recently, there has been increased interest in providing reed diffuser fragrance formulations that are environmentally friendly. Currently, the majority of reed diffuser formulations use industrial organic solvents such as petroleum distillates and other volatile organic compounds (VOC), which are restricted by CARB (California Air Resources Board). In addition to meeting governmental regulations, reducing or eliminating the use of these solvents would greatly enhance the environmental friendliness of the reed diffuser fragrance formulations. One method to achieve this goal is to use water, instead of organic solvents, as the base of the reed diffuser fragrance formulations. With the aid of surfactants to dissolve the fragrance in water this can be achieved. However, wooden reed diffusers are not compatible with water based formulations. When water based formulations are used with wooden reed diffusers the diffusers become water-logged and, consequently, the wicking rate is severely reduced. In addition to retarding the wicking rate, the water encourages the growth of mold and mildew on the wooden diffusers and causes them to decay. Likewise, conventional porous ceramics do not perform adequately with water based formulations, because their low wicking rate renders them virtually unusable as fragrance diffusers.
In short, the main limitations of the current technology, whether it be wooden diffusers or conventional porous ceramics, is their low wicking rates and inability to effectively utilize water-based fragrance formulations. To overcome the limitations associated with natural reed and conventional porous ceramic fragrance diffusers, a wick made of a network matrix ceramic having a high wicking rate with aqueous, water-based formulations as well as non-aqueous organic formulations, and having higher strength than conventional porous ceramics, was developed. The present invention is directed to such a wick.